Problem: The perimeter of a square is $12$ units. How long is each side?
Explanation: $\text{? }$ The perimeter is the total length of all the sides of the shape added together. $ {\text{?}} + {\text{?}} + {\text{?}} + {\text{?}} = 12\text{ } $ $ {3} + {3} + {3} + {3} = 12\text{ } $ The sides of a square are all the same length, so each side must be $3$ units long.